Delta 9 Tetrahydrocannabinol (THC) has been shown in previous clinical observations to ameliorate nausea and vomiting associated with chemotherapy. This current double blind, placebo controlled study is designed to assess the antiemetic efficacy of THC in cancer patients undergoing intensive chemotherapy. In addition, since THC can alter hepatic-microsomal drug metabolism of certain drugs as evidenced by induced tolerance to THC this study examines the effects of THC on the plasma pharmacokinetics of antineoplastic agents.